1. The Field of Invention
The present invention relates generally to the field of disc drive storage, and more particularly to lubricants used in disc drives to improve tribological properties.
2. Description of the Related Art
Computer disc drives commonly use components made out of thin films to store information. Both the read-write element and the magnetic storage media of disc drives are typically made from thin films.
FIG. 1 is an illustration showing the layers of a conventional magnetic media structure including a substrate 105, a seed layer 109, a magnetic layer 113, a diamond like carbon (DLC) protective layer 117, and a lube layer 121. The initial layer of the media structure is the substrate 105, which is typically made of nickel-phosphorous plated aluminum or glass that has been textured. The seed layer 109, typically made of chromium, is a thin film that is deposited onto the substrate 105 creating an interface of intermixed substrate 105 layer molecules and seed layer 109 molecules between the two. The magnetic layer 113, typically made of a magnetic alloy containing cobalt (Co), platinum (Pt) and chromium (Cr), is a thin film deposited on top of the seed layer 109 creating a second interface of intermixed seed layer 109 molecules and magnetic layer 113 molecules between the two. The DLC protective layer 117, typically made of carbon and hydrogen, is a thin film that is deposited on top of the magnetic layer 113 creating a third interface of intermixed magnetic layer 113 molecules and DLC protective layer 117 molecules between the two. Finally the lube layer 121, which is a lubricant typically made of a polymer containing carbon (C) and fluorine (F) and oxygen (O), is deposited on top of the DLC protective layer 117 creating a fourth interface of intermixed DLC protective layer 117 molecules and lube layer 121 molecules.
The durability and reliability of recording media is achieved primarily by the application of the DLC protective layer 117 and the lube layer 121. The DLC protective layer 117 is typically an amorphous film called diamond like carbon (DLC), which contains carbon and hydrogen and exhibits properties between those of graphite and diamond. Thin layers of DLC are deposited on disks using conventional thin film deposition techniques such as ion beam deposition (IBD), plasma enhanced chemical vapor deposition (PECVD), magnetron sputtering, radio frequency sputtering or chemical vapor deposition (CVD). During the deposition process, adjusting sputtering gas mixtures of argon and hydrogen varies the concentrations of hydrogen found in the DLC. Since typical thicknesses of DLC protective layer 117, are less than 100 Angstroms, lube layer 121 is deposited on top of the DLC protective layer 117, for added protection, lubrication and enhanced disk drive reliability. Lube layer 121 further reduces wear of the disc due to contact with the magnetic head assembly.
Although conventional lubricants have been used to lubricate disks in hard drive applications, there are problems with using conventional lubricants in media for modern disc drives applications. For example, modern media use much thinner layers and much thinner lubricants than older media from just a few years ago and as the thickness of the protective layers 117 and lube layers 121 are reduced, reliability problems arise. A more integrated protection structure is needed that will produce a more durable protective film without effecting thicknesses. Reliability of hard disks is heavily depended upon the durability of the thin film media.
Lubrication additives, such as Bis(4-fluorophenoxy)-tetrakis(3-trifluoromethyl phenoxy)cyclotriphosphazene (X1P), have been used to improve tribological performance and corrosion resistance of thin film media. Although these new lubricant that contain additives are an improvement over old lubricants, there are still many tribological problems associated with them including lubricant pick-up, head smear, high stiction, and other problems resulting from weak bonding of the lubricant and carbon-containing overcoat. Additionally, since lubricants contain ingredients, that deteriorate tribological performance, if allowed to build up on the medium, the chemical compositions of both the lube bath and lubricant film on the medium must be closely monitored to prevent unexpected fall-off of tribological performance.
Therefore what is needed is a lubricant that overcomes these problems, provides better tribological performance and provides desirable properties. Desirable properties include a resulting lubricant that does not have problems such as phase separation, lubricant pick-up, head smear, high stiction, etc.